Catheters are tube-like members inserted into the body for diagnostic or therapeutic reasons. One of the therapeutic procedures applicable to the present invention is known as percutaneous transluminal coronary angioplasty (PTCA). This procedure can be used, for example, to reduce arterial build-up of cholesterol fats or atherosclerotic plaque. If, during the procedure, a catheter must be exchanged for one of a different size, an over-the-wire system is advantageous because the guidewire can be left in place. In over-the-wire systems, the guidewire is threaded through the vascular system to the site of the stenosis and the catheter subsequently tracked over it to the stenosis. The catheter is withdrawn over the guidewire and another catheter can be slid into place over it. If both the catheter and the lumen have a round shape, with substantially equal diameters, tracking can be diminished due to friction between the catheter and the guidewire. In areas where the catheter body is flexed, the lumen wall will deform and contact a substantial percentage of the circumference of the guidewire. Various alternative designs have been proposed to form noncircular lumens. Lumen tubing having noncircular lumens is known in the art as follows.
U.S. Pat. No. 3,995,623, to Blake et al, for "Multipurpose Flow-Directed Catheter", discloses in FIG. 5 a balloon flotation electrode catheter with four noncentrally located, noncircular lumens. The lumens are pie shaped with each having two generally planar, longitudinally extending wall surfaces joined at about a 90 degree angle with those two walls joined by a third curved wall as measured in cross-section. The outer wall thickness is substantially constant.
U.S. Pat. No. 4,328,806, to Cooper, for "Catheter with Trans-Luminal Gas Pathway", discloses in FIGS. 4-6 and FIGS. 9-10, a catheter having at least two separate noncentrally located, noncircular lumens of a pie shape. One lumen is for conveying liquids to and from a port spaced substantially from the distal end of the catheter and the other for enclosing an electrical conductor. The lumens are pie shaped with each having two generally planar, longitudinally extending wall surfaces joined at more than a 90 degree angle with those two walls joined by a third curved wall as measured in cross-section. The outer wall thickness is substantially constant.
U.S Pat. No. 4,632,108, to Geil, for "Tube and Material for Use in Laser Surgery", discloses in FIG. 2, a laser-resistant surgical tube for use in connection with laser surgery, with a centrally located, noncircular first conduit having two generally planar, longitudinally extending wall surfaces joined at about a 90 degree angle, with those two walls joined by a third curved wall as measured in cross-section. The outer wall thickness is substantially constant.
U.S Pat. No. 4,753,640, to Nichols, et al., for "Catheters and Methods", discloses in FIGS. 1-9, a catheter assembly with one or more lumens having D-shaped axial lumens with linear wall surfaces joined tangentially. At least one longitudinally extending wall surface is curved when measured in cross-section.
U.S Pat. No. 4,947,852, to Nassi, et al., for "Apparatus and Method for Continuously Measuring Volumetric Blood Flow using Multiple Transducer and Catheter for use Therewith", discloses in FIG. 2, a noncentrally located guidewire lumen with an even number of walls of constant thickness.
U.S Pat. No. 5,271,410, to Wolzinger, et al., for "Catheter with Rapid Response Thermistor and Method", discloses in FIG. 2, four noncircular, noncentrally located lumens. At least one longitudinally extending wall surface is curved when measured in cross-section. The outer wall thickness is substantially constant.
Commonly owned copending application Ser. No. 07/944,756, to Molacek, et al for a Medical Electrical Lead discloses in FIG. 2, a multilumen lead with generally rounded-corner triangular or "pie-shaped", noncentrally located lumens in cross-section. The outer wall thickness is substantially constant as the minimum wall thickness for adequate electrical isolation between the lumens imposes a design constraint on such leads. Increases in diameter of a circular lumen result in increases in achievable minimum lead diameter.
Single lumen catheters are typically circular in shape and have a constant wall thickness thereby maximizing the lumen inner diameter while minimizing the lumen outer diameter. This permits the largest guidewire to fit in the catheter with the smallest outer diameter. Multilumen catheters are often pie shaped and have a constant wall thickness as this tends to permit the greatest number of lumens in the smallest area. Catheter walls collapse when submitted to high levels of stress. Friction results when the guidewire comes in contact with the lumen walls. The object of the invention is to create a lumen with a wall configuration which will tolerate higher levels of stress yet result in minimum friction between the guidewire and inner lumen.